Deformation and stress concentration appearing during high-temperature sintering process significantly affect production quality of solid oxide cell (SOC), due to mismatched mechanical and thermophysical properties of the sintered electrode and electrolyte. In this study, a coarse-grained molecular dynamics (CG-MD) method is developed to evaluate and correlate coefficient of thermal expansion (CTE) and elastic modulus during the entire co-sintering process (including temperature-increasing, −insulation, and -decreasing stages). It is revealed that, in the sintered porous cermet electrode, CTE primarily exhibits an increasing trend until temperature-decreasing stage. Compared to the constant values commonly applied in the literature, the elastic modulus experiences a decay trend with a reduction of 32.14 % in the porous electrode and 9.68 % reduction in the dense electrolyte. The obtained CTE and elastic modulus are correlated with the sintering parameters and further applied to a macroscopical model for predicting overall sintering warpage and stress in a co-sintered SOC half-cell composed of a thick porous electrode and a thin dense layer. The varied CTE is identified as the main factor influencing warpage deformation, while the elastic modulus as a more significant impact on the von Mises stress during the co-sintering of the half-cell. Analysis is further conducted by orthogonal testing method for sintering temperature, sintering time, material content and diameter ratio of the porous cermet nanoparticles, aiming to optimize the varied CTE and elastic modulus, particularly during the temperature-insulation process. Subsequently, the optimized properties are implemented, and it is found that, after sintering insulation for 120 min, the maximum warpage displacement is about 7.34 mm, which represents a decrease of approximately 14.11 %; while the von Mises stress is observed to be 379.24 MPa, which indicates a reduction of around 37.33 % compared with the predictions by the constant properties.
Read full abstract